Jiajun Wang, Jun Wang*
National Synchrotron Light Source II, Brookhaven National Laboratory, Building 743 Ring Road, Upton, NY (USA)
Electrochemically driven phase transformation directly influences electrode performance in lithium ion batteries. Advancing our understanding of the mechanism necessitates the development of advanced tools with in situ capability to track the dynamic phase and structural changes of battery materials at 2D and 3D. The synchrotron hard X-ray imaging technique is particularly interesting for applications in battery studies because of its natural characteristics: it is non-destructive, chemically and elementally sensitive, environmentally friendly, and highly penetrative to enable in situ study of a real battery. Considerable progress in this field has been reported recently from our group, beamline X8C at the National Synchrotron Light Source (NSLS) at Brookhaven National Laboratory (BNL), where a new hard X-ray imaging technique, transmission X-ray microscopy (TXM), has been developed and applied to battery microstructure study.
TXM is a full-field high resolution x-ray imaging technique with a Fresnel zone plate serving as an objective lens. The newly developed TXM at BNL has offered new opportunities to directly image the interior microstructures of a variety of battery materials in 2D and 3D at nanometer scale.[1-5] A particularly important capability of this new beamline is that it can provide chemical phase mapping information at nano-scale spatial resolution (sub-30 nm for 2D and sub-50 nm for 3D), combining with X-ray absorption near edge structure (XANES) spectroscopy. The absorption mode (5-11 keV) covers most of transition-metal elements (e.g. Zn, Cu, Fe, Co, Ni, Mn, etc), which is particularly interesting for batteries, catalysts and other energy materials studies. The large field of view (40x40 µm) allows observing many particles in the sample at the same time, which will provide more accurate statistic information.
In this talk, we will present our recent work using in situ/in operando TXM approach to track phase transformation at 2D and 3D for anode (Tin) and cathode (LiFePO4) battery materials. Challenges and opportunities of TXM technology for energy materials research will be also discussed. This in situ imaging approach has a wide variety of applications in other fields, such as fuel cells, catalysis, environmental science and biological science.
Reference
[1] Wang, J., Eng, C., Chen-Wiegart, Y. K., Wang, J. Probing three-dimensional sodiation–desodiation equilibrium in sodium-ion batteries by in situ hard X-ray nanotomography. Nat. Commun. 6, 7496 (2015).
[2] Wang, J., Chen-Wiegart, Y. K., Wang, J. In operando tracking phase transformation evolution of lithium iron phosphate with hard X-ray microscopy. Nat. Commun. 5, 4570 (2014).
[3] Wang, J., Chen-Wiegart, Y. K., Wang, J. In situ three-dimensional synchrotron X-ray nanotomography of the (de)lithiation processes in tin anodes. Angew. Chem. Int. Ed. 126, 4549-4553 (2014).
[4] Wang, J. et al. Size-dependent surface phase change of lithium iron phosphate during carbon coating. Nat. Commun. 5, 3145 (2014).
[5] Wang, J., Chen-Wiegart, Y. K., Wang, J. In situ chemical mapping of a lithium-ion battery using full-field hard X-ray spectroscopic imaging. Chem. Commun. 49, 6480-6482 (2013).
[6] Wang, J. et al. Automated markerless full field hard x-ray microscopic tomography at sub-50 nm 3-dimension spatial resolution. Appl. Phys. Lett. 100, 143107 (2012).